Method and apparatus for recovery of a slick floating on the surface of a liquid

ABSTRACT

Method and apparatus for recovery of the product forming a slick floating on the surface of the water such as an oil slick. The apparatus comprises  
     a recovery head ( 1 ) formed by an enclosure ( 2 ) having in the upper part an inlet ( 3 ) for the product to be recovered and in the lower part ( 4 ) an outlet for the recovered product, as well as a vortex generator which creates in the enclosure a dynamic vortex (V) which descends in the enclosure ( 2 ) as far as its outlet ( 4 ),  
     a flotation means ( 5 ) which supports the enclosure ( 2 ) so as to keep its inlet ( 3 ) at the level of the slick to be recovered,  
     a pipe ( 20 ) connecting the outlet of the enclosure to a tank ( 31 ).

[0001] The present invention relates to a method and to apparatus forrecovery of a slick floating on the surface of the water such as an oilslick.

[0002] Different methods and apparatus are known for recovering theproduct from a slick floating on the surface of the water and, inparticular, an oil slick floating at sea.

[0003] The known methods and apparatus are very varied, ranging fromfloating booms to floating storage or recovery devices. The recoverydevices are classified into two types, the mechanical recovery devicesmaking use of the fluid flow properties and the density of the liquid tobe recovered and the oleophilic recovery devices being intended moreparticularly for the recovery of oil and using the properties ofadhesion of the oil on surfaces which are brought into contact with thewater and the pollutant.

[0004] This classification is published in a study by CEDRE (Centre dedocumentation de recherche et expérimentations sur les pollutionsaccidentelles des eaux) entitled “La récupération du pétrole en mer”(extract from the INFOPOL course organised by CEDRE in 1999).

[0005] The mechanical recovery devices use either direct suction orsuction with a spillway or even a simple conveyor belt or a conveyorbelt working by submersion.

[0006] The oleophilic recovery devices consist in general of an assemblyof discs, drums or equipment having belts or ropes, which penetrate intothe slick and take advantage of the adhesion of the oil on the structureof the discs, the belts or the ropes in order to catch the productthere, to transport it and to discharge it. It is generally removed byscraping or squeezing.

[0007] Amnongst the mechanical recovery devices there is one known as avortex recovery device formed by a pumping head or strainer which comesover the slick to be pumped, at the level of the slick. Below thepumping head, a agitator creates a depression by forming a static vortexin such a way as to accumulate the product which is less dense than thewater in order to concentrate it below the strainer.

[0008] In fact, this apparatus uses a agitator in order to create apocket in which the liquid to be pumped accumulates below the suctionhead.

[0009] According to the analysis made in this document and summarisingthe tests, this apparatus is very delicate to use and is only suitablefor fluid products in calm waters. This method and this apparatus do notallow partially solid products to be pumped because the pumping is donefrom above in the opposite direction to the direction in which thestatic vortex creates the depression forming the pocket.

[0010] In other words, the static vortex and the suction effect ofpumping act in opposite directions.

[0011] This method cannot be used when the surface of the water isagitated because then the penetration of air into the pumping head risksstopping the pump.

[0012] The object of the present invention is to remedy the drawbacks ofthe known solutions and the invention proposes the development of amethod and an apparatus permitting pumping in an extremely efficientmanner of slicks of product floating on the surface of the water,regardless of the physical nature of the products (fluid, semi-fluid oreven partially solidified state), and regardless of the characteristicsof the location of the floating slick, whether this location is subjectto the swell, the wind, to surface currents, or indeed the locationwhere the slick is situated.

[0013] To this end the invention relates to a method characterised inthat

[0014] a dynamic vortex is created below the surface of the floatingslick,

[0015] this vortex is supplied with the slick whilst practicallyretaining the liquid on which the product is floating,

[0016] the product is discharged via the base of the dynamic vortex.

[0017] The vortex according to the invention causes the flow of producttaken from the slick to circulate in order to discharge it, this flowpossibly being taken up by a pump connected to the outlet of the vortex.

[0018] This suction will then be added to the surge communicated to thefluid in the region of the vortex.

[0019] The recovery of the product may be carried out in a manner verylargely independent of the physical nature of the recovered product,regardless of whether the product is liquid, more or less pasty or evencontains solid particles or parts.

[0020] The method permits recovery even of solid particles floating onthe surface of the slick, since these particles will be entrained in thevortex and discharged from there.

[0021] The invention also relates to a recovery apparatus of the typedefined above, characterised in that it comprises:

[0022] a recovery head formed by an enclosure having in the upper partan inlet for the product to be recovered and in the lower part an outletfor the recovered product, as well as a vortex generator which createsin the enclosure a dynamic vortex which descends in the enclosure as faras its outlet,

[0023] a flotation means which supports the enclosure so as to keep itsinlet at the level of the slick to be recovered,

[0024] a pipe connecting the outlet of the enclosure to a tank.

[0025] The dynamic vortex generator is advantageously a agitatorimmersed in the enclosure and borne by the shaft of a motor.

[0026] Regardless of whether it is a question of the method or of theapparatus, in both cases there is a dynamic vortex, that is to say avortex which produces a fluid circulation from top to bottom, from theinlet of the recovery device to its outlet, and not a simple staticdepression creating a pocket filled with product of lesser density thanthat of the liquid in which the slick of product normally floats, thatis to say fresh water or sea water.

[0027] The agitator which creates the vortex is advantageously immersedat an adjustable height in the enclosure of the floating slick, whichenables the vortex effect to be adapted to the nature of the products tobe recovered.

[0028] The enclosure is advantageously in the shape of a funnelfollowing the flow lines of the vortex, the flared portion of theenclosure constituting the product inlet, whilst the tip of the coneconstitutes the outlet connected to the discharge pipe.

[0029] This shape of the enclosure like a funnel favours the flow of theproduct slick in the vortex without creating dead zones which would beoccupied by the product or by water.

[0030] The outlet of the enclosure is advantageously connected to adischarge pipe equipped with a suction means. This discharge pipe mayhave a certain length as a function of the arrangement of the differentmeans of the apparatus and notably of the recovery head and the tasksfor collecting the product.

[0031] In the case of a discharge pipe connected to a suction means suchas a pump, it is advantageous for a control unit to be connected to themotor of the vortex generator and to the suction means in order toco-ordinate the operation of these two means and to permit optimumoutput.

[0032] The flotation means is advantageously formed by floats supportingthe enclosure and the vortex generator. This flotation means does notconstitute a closed barrier placed above the enclosure or surroundingthe latter. On the contrary, it is solely a matter of separate points ofsupport leaving passages between them to enable not only the slick butalso the surface of the slick to penetrate into the enclosure in orderto be taken up by the vortex.

[0033] In these circumstances it is particularly advantageous for theconnection between the floats and the enclosure to be adjustable, whichallows the depth of immersion of the inlet of the enclosure to beadjusted as a function of the thickness of the slick of product to berecovered.

[0034] This floating placement of the apparatus makes it possible tofollow the variations of height of the slick, particularly as a functionof the swell.

[0035] Generally speaking, the method and the apparatus according to theinvention constitute means which are extremely simple to implement,capable of operating in extreme conditions both as regards the situationof the slick to be recovered and the nature of the products.

[0036] Finally, the apparatus is particularly simple to maintain and toput into operation and it is not very cumbersome.

[0037] The present invention will described below in greater detail withthe aid of the accompanying drawings, in which:

[0038]FIG. 1 shows a diagram of a known apparatus,

[0039]FIG. 2 shows a diagram of the apparatus according to theinvention,

[0040]FIG. 3 shows a detail of the apparatus according to FIG. 2,

[0041]FIG. 4 shows the apparatus according to the invention in theoperating position.

[0042] According to FIG. 1 a known apparatus of the vortex type formechanical recovery of the product P floating in the form of a slick onthe surface of the water E is composed of a suction head 100 placed onthe surface of the slick P. This suction head 100 has a agitator 101driven by a motor (not shown) and is accommodated in a trumpet-shapedcaisson 102 surrounding the agitator 101. The agitator 101 creates adepression in the interior of the caisson 102 in order to form a pocket103 below the inlet 104 of the suction head 100 so that a layer ofproduct P accumulates there, permitting pumping. The product P is pumpedas indicated by the arrows F1, F2.

[0043] In this known apparatus the agitator 101 creates a sort of staticvortex forming the pocket in which the product P accumulates; thislatter can then be sucked up. However, as already indicated, thissuction is opposed to the suction created by the static vortex.

[0044] The present invention relates to an apparatus such as that shownin FIGS. 2 and 3 and in the operating position in FIG. 4.

[0045] According to FIG. 2, the apparatus is composed of a recovery head1 formed by an enclosure 2 having an inlet 3 in the upper part and anoutlet 4 in the lower part. This head 1 is borne by a flotation meansconsisting of floats 5 which are integral with a chassis 6. The chassis6 also bears a motor 7, the shaft 8 of which is equipped with a agitator9 which constitutes a vortex generator. This agitator 9 creates adynamic vortex in the enclosure 2 which is preferably in the shape of atrumpet according to the flow lines of a vortex.

[0046] The enclosure 2 is connected to the frame 6 by means ofconnecting devices 10 of adjustable length. These connecting devices areshown connected to the floats 5. They could equally be connecteddirectly to the frame 6. These connecting devices 10 of adjustablelength permit modification of the depth (e) of immersion of the edge ofthe enclosure 2 which constitutes the inlet 3. This adjustment is madeas a function of the thickness X of the slick of product P to berecovered (see FIG. 3).

[0047] As adjustment means there is provided, in this particularexample, a threaded rod 11 connected to the float 5 and equipped with anut 12 in order to hold the edge 13 of the enclosure 2. Thus the height(e) of the opening 3 is defined.

[0048]FIG. 4 shows the apparatus according to the invention in theposition of use.

[0049] The recovery head is placed in a slick of product P and issupported on the slick, and more generally on the surface of the liquid,by means of its floats 5. These floats 5 do not constitute a ringsurrounding the top of the enclosure 2 but rather they form supportsdistributed over the surface of the slick or of the liquid as isindicated in FIG. 4 in which, by contrast with FIG. 2, the left-handfloat 5 has not been shown.

[0050] It is extremely important that the float or floats 5 do notconstitute a closed barrier extending over the top of the inlet of theenclosure 2 so as not to force the slick of product P to passnecessarily under all of the floats 5.

[0051] On the contrary, and as shown in the right-hand part of FIG. 4,more or less solid products P1 can themselves float on the surface ofthe slick P. These may be particles P1 of more or less solidifiedproducts. All these particles, even floating on the surface, canpenetrate into the enclosure 2, sucked up by the dynamic vortex createdby the agitator 9.

[0052] This means that the agitator 9 creates not only a depression inthe enclosure 2 but a vortex V, shown schematically in FIG. 4, whichgoes at least as far as the outlet 4 of the enclosure 2.

[0053] This dynamic vortex sucks the upper layer of the liquid in whichthe recovery head 1 is floating and which is principally constituted bythe slick of product P.

[0054] The outlet 4 of the enclosure 2 is connected to a pipe 20 for thedischarge of the product. This pipe 20 is preferably connected to a pump30 which discharges the liquid to a tank 31.

[0055] Thus according to the method according to the invention forrecovery of the product forming a slick on the surface of the water,such as an oil slick, a dynamic vortex is created below the surface ofthe floating slick; this vortex is supplied with the slick, principallyretaining the liquid on which the product to be recovered is floatingand the product is discharged, possibly with liquid, via the base of thevortex.

[0056] This discharge is carried out in the same direction of action asthat of the vortex.

[0057] In particular, the product is sucked, possibly with liquid, atthe base of the vortex. This suction is added to the effect of suctionor of pressure of the vortex. This method permits recovery of theproduct P floating on the surface of the liquid E, practicallyregardless of the state of the product P, liquid, more or less viscousand even containing solid particles. Even if the surface of the slick ofproduct P is more or less agitated, this slick can be recoveredefficiently by the active vortex.

1. Apparatus for recovery of the product forming a slick floating on thesurface of the water such as an oil slick, characterised in that itcomprises: a recovery head (1) formed by an enclosure (2) having in theupper part an inlet (3) for the product to be recovered and in the lowerpart (4) an outlet for the recovered product, a vortex generator whichis formed by a agitator (9) immersed in the enclosure and borne by theshaft (8) of a motor (7) and which creates in the enclosure a dynamicvortex (V) which descends in the enclosure (2) as far as its outlet (4),a flotation means (5) which supports the enclosure (2) so as to keep itsinlet (3) at the level of the slick to be recovered (8), a pipe (20)connecting the outlet of the enclosure to a tank (31).
 2. Apparatus asclaimed in claim 1, characterised in that the agitator (9) is immersedat an adjustable height in the enclosure below the level of the floatingslick (P).
 3. Apparatus as claimed in claim 1, characterised in that theenclosure (2) is in the shape of a funnel following the flow lines ofthe vortex, the flared portion of the enclosure constituting the productinlet (3), whilst the tip of the cone constitutes the outlet (4)connected to the discharge pipe (20).
 4. Apparatus as claimed in claim1, characterised in that the discharge pipe (20) is connected to asuction means (30).
 5. Apparatus as claimed in any one of claims 1 and4, characterised by a control unit connected to the motor (7) of thevortex generator (7, 8, 9) and to the suction means (30) in order tocontrol these two means as a function of one another.
 6. Apparatus asclaimed in claim 1, characterised in that the flotation means (5) isformed by floats supporting the enclosure (2) and the vortex generator(7, 8, 9).
 7. Apparatus as claimed in claim 6, characterised in that theconnection (10) between the floats (5) and the enclosure (2) isadjustable in order to adjust the depth of immersion of the inlet (3) ofthe enclosure as a function of the thickness (X) of the slick of productto be recovered (P).